1) Field of the Invention
The present invention relates to a system and method for ejecting stores from an aircraft and, more particularly, to a store ejection system and method that use a pressure vessel of pressurized non-pyrotechnic gas for providing the source of energy and the transfer mechanism to eject the stores from the aircraft.
2) Description of Related Art
The term xe2x80x9cstorexe2x80x9d is used herein to refer generally to any of a number of munitions or other materials that can be dispensed from an aircraft. For example, military aircraft can include a store ejection system to dispense bombs, missiles, rockets, and other types of munitions. Non-munitions stores can include electronic equipment and other materials. Typically, the store ejection system includes one or more racks beneath the wings or fuselage of the aircraft for holding the stores and releasing the stores upon a command. For example, store racks are described in U.S. Pat. Nos. 5,907,118 and 6,035,759, both by the same inventor and assignee as the present invention.
In one conventional store ejection system, the stores are connected to the racks by one or more mechanical hooks. The store ejection system includes a release mechanism for actuating the hooks to release the stores and a jettison mechanism for forcibly ejecting the stores away from the aircraft. The jettison mechanism can include a pressure-actuator, such as a ram that is actuated by a pressure increase in a cylinder. In the conventional system, the pressure is generated by a pyrotechnic cartridge, i.e., an explosive. Ignition of the pyrotechnic cartridge initiates a chemical reaction that generates a high pressure, which can be used for actuating the release mechanism and the jettison mechanism.
Although such pyrotechnic cartridges provide a weight efficient unit for storing and releasing energy, the cartridges present a number of maintenance, reliability, and safety concerns. For example, the chemical reaction of the explosive charge in the cartridge generates a large amount of residue. Some of the residue is deposited in the ejection system where it can clog or otherwise interfere with the components of the ejection system. Moisture and corrosives in the residue can also damage the ejection system. Additionally, moisture deposited in the ejection system can freeze or gather additional debris. To avoid unreliability and possible failure, the ejection system must be disassembled and cleaned regularly, thus increasing the cost and downtime for maintaining the system. Such cleaning often requires the use of hazardous cleaning solvents that require care in storage, use, handling, and disposal. Further, due to the pyrotechnic nature of the cartridges, special storage and handling precautions for the cartridges are necessary. For example, ground crew personnel must use special equipment to conduct stray voltage checks before installing the cartridges to prevent inadvertent firing. Also, unspent cartridges must be removed before unloading unreleased stores from the aircraft.
Non-pyrotechnic ejection systems have been proposed, such as the pneumatically-driven store ejection system described in U.S. Pat. No. 5,583,312, which is also by the same inventor and assignee as the present invention. That device does not require pyrotechnic cartridges, but instead includes a compressor for compressing a non-pyrotechnic gas that is then used to actuate ejector pistons of one or more suspension and release equipment (S and RE) modules that releasably retain and jettison stores. The pressurized gas, which can comprise ambient air, does not deposit a significant amount of residue on the system components. Thus, the residue build-up and corrosion resulting from pyrotechnic chemicals are eliminated and the maintenance required on the system is minimized. However, the compressor adds to the initial cost of the system and the recurring costs for overhauling and maintaining the compressor. The compressor also adds to the overall weight of the system. Further, the compressor requires the availability of sufficient power from the aircraft""s electrical or hydraulic systems to drive the compressor motor. In addition, the compressor must generate sufficient pressure to release the stores, so the compressor requires an interval of time for preparing the release of the store. The time required to achieve a sufficient pressure is dependent on the compressor, the number and size of ejector racks that are connected to the system, and the air density, which varies with altitude. Therefore, the release of the stores can be delayed while the compressor generates the required pressure.
There have also been proposed ejector devices that use a stored volume of compressed gas to provide the energy for ejection. For example, U.S. Pat. Nos. 4,095,762 and 4,905,568 to Holt and Hetzer et al., respectively, each describe an ejector mechanism that uses a pressurized gas as the energy source for ejection and a hydraulic fluid, which acts as the energy transfer mechanism for ejection. Both patents describe that the hydraulic fluid can be used to re-pressurize the gas after ejection. Holt specifies that the action of recocking a piston moves the hydraulic fluid and thereby re-pressurizes the gas. Hetzer recites that after ejection, a pump is used to pump the hydraulic fluid, and the hydraulic fluid thereby acts on the gas to re-pressurize it. Therefore, neither patent requires a compressor for re-pressurizing the gas. However, the hydraulic systems add weight and complexity to the system. Further, the pump of Hetzer for pumping the hydraulic fluid adds weight, power, and timing concerns similar to those discussed above in connection with the compressor of U.S. Pat. No. 5,583,312. Similarly, in the case of Holt, some additional device would be required for recocking the system.
U.S. Pat. No. 4,204,456 to Ward discloses a pneumatic bomb ejector that uses a pressurized gas from a storage container for the energy required to eject the bomb. However, no specific storage container is described, and there is no description regarding how and when the storage container is pressurized. Pressurizing the container during flight would require a pressurization device, such as a compressor, again with the weight, power, and timing concerns noted above. Alternatively, if the storage container is pre-pressurized before the aircraft takes off so that no on-board compressor is needed, the pressure in the storage container will fluctuate as the temperature of the gas in the storage container changes with the ambient temperature. Further, the pressure in the storage container will not be affected by changes in the ambient pressure. Thus, the differential in pressure between the storage container and the ambient air will change as the aircraft changes altitude, thereby changing the operational characteristics of the ejector and possibly resulting in incorrect or failed ejections. Additionally, refilling the container before take-off would require that the container be connected to a refilling device, which could delay the flight.
Thus, there is a need for a store ejection system and method that use a non-pyrotechnic gas as the source of energy and transfer mechanism for jettisoning a store from an aircraft. The system should not require the use of pyrotechnic reactions or an on-board compressor system. Preferably, the system should not require a long time delay to achieve pressurization. Additionally, the system should require little or no power from the aircraft""s electrical or hydraulic systems for pressurizing the gas.
The present invention provides a store ejection system and method that use a non-pyrotechnic gas as the energy and transfer mechanisms for jettisoning a store from an aircraft. The gas is held pressurized in an on-board pressure vessel so that no pyrotechnic reaction or on-board compressor is required for pressurization, thereby simplifying system maintenance, complexity, weight, and ejection timing. A pressure regulator controls the pressure of the gas delivered from the pressure vessel, even when ambient conditions vary. Further, the pressure vessel is releasably connected to the pressure regulator, and can therefore be removed after use for quick replacement or refilling. A releasable seal on the pressure vessel provides a hermetic seal until the pressure vessel is connected to the pressure regulator and the seal is released.
According to one embodiment of the present invention, a store ejection system is provided for mounting at least one jettisonable store on an aircraft. An on-board pressure vessel of pressurized non-pyrotechnic gas provides the source of energy and the transfer mechanism. According to one aspect of the invention, the pressure vessel defines an interior space of between about 10 and 250 cubic inches, and the pressure vessel can be pressurized to between about 3000 and 10,000 psi.
A releasable seal, which can be released from a closed position to an open position, is configured to hermetically seal the pressure vessel. The releasable seal can include, for example, a valve or a burst portion that can be destructively released, and the seal can be released by an actuator. The releasable seal is also fluidly connected to a pressure regulator. The pressure regulator controls a flow of the gas from the pressure vessel when the releasable seal is open. The releasable seal is configured to be released after the pressure vessel is connected to the pressure regulator so that the seal hermetically seals the pressure vessel before the pressure vessel is connected to the pressure regulator. According to one aspect of the invention, the releasable seal is configured to be released upon connection of the pressure vessel to the pressure regulator.
The ejection system also includes at least one actuation system and at least one pneumatically-driven jettison mechanism. Each actuation system includes an accumulator that is fluidly connected to the pressure regulator. The accumulator receives and stores the gas from the pressure vessel at a specified operating pressure. A dump valve, which controls the flow of gas from the accumulator, is actuated by a controller so that the dump valve can be opened in response to a control signal to jettison the store.
According to another aspect of the invention, the pressure regulator is adapted to control the flow of the gas from the pressure vessel and thereby maintain the specified operating pressure in the actuation system. According to yet another aspect, each actuation system includes a relief valve for venting the gas from a respective accumulator of each actuation system.
The jettison mechanisms, which releasably retain the stores, are fluidly connected to the dump valves so that actuating each dump valve to an open position releases the pressurized gas in a respective accumulator to flow to a respective jettison mechanism, thereby actuating the jettison mechanism to jettison the respective store. Each jettison mechanism can include at least one hook for releasably retaining the store, the hooks being actuated to release the store from the jettison mechanism by the pressurized gas exiting a respective accumulator through a respective dump valve. Additionally, each jettison mechanism can also include at least one ejector piston for forcibly jettisoning the store away from the aircraft when the hook has been actuated to a release position. The at least one ejector piston is also actuated to jettison the store by the pressurized gas exiting the accumulator through the dump valve.
According to one aspect of the invention, the ejection system includes a plurality of jettison mechanisms, a corresponding plurality of actuation systems, and a manifold line that fluidly connects the pressure vessel to each actuation system. A plurality of enable valves can also be provided. Each enable valve is fluidly connected to the manifold line and configured to control the flow of the gas from the pressure regulator to a respective actuation system.
The present invention also provides a method of ejecting stores from an aircraft using a gas as the source of energy and the transfer mechanism. The method includes releasably retaining at least one store with at least one pneumatically-driven jettison mechanism. An on-board pressure vessel of pressurized non-pyrotechnic gas is releasably connected to a pressure regulator. The pressure vessel can be pressurized and hermetically sealed with a releasable seal prior to its connection. The releasable seal of the pressure vessel is released such that the pressure vessel is fluidly connected to the pressure regulator. The seal can be released by destructively releasing a burst portion of the seal, for example, while connecting the pressure vessel to the pressure regulator. The pressure regulator is configured to an open configuration such that the gas flows from the pressure vessel to at least one accumulator fluidly connected to the pressure regulator, for example, to pressurize the accumulator to a specified operating pressure. A dump valve fluidly connected to one of the accumulators is actuated to an open position to fluidly connect the accumulator to one of the jettison mechanisms such that the gas flows from the accumulator to the jettison mechanism and thereby actuates the respective jettison mechanism to jettison a store. For example, the accumulator can be fluidly connected to at least one ejector piston such that the gas flowing from the accumulator actuates the at least one ejector piston to jettison the store. Each store can also be releasably retained with at least one hook, which is opened during the actuating step to release the store.
According to one aspect of the invention, the pressure regulator is opened when at least one of the accumulators requires pressurization to attain the specified operating pressure and closed when the specified operating pressure is attained. According to another aspect, a relief valve fluidly connected to one of the accumulators is opened to vent the gas from the respective accumulator when an over-pressure condition is detected in the respective accumulator or when it is desired to disarm a respective jettison mechanism.
After the dump valve has been actuated, the pressure vessel can be released from the pressure regulator and repressurized, followed by a repetition of the connecting, releasing, configuring, and actuating steps.